This is caused by the escalation policy snapshot. The snapshot is taken when the incident is first triggered, and because your user or schedule was being used on the escalation policy when it was triggered, they are associated with it until it is resolved…
That means that even if you don’t see any incidents assigned to that user or using that schedule, they are still stuck on the escalation policy snapshot, which is intended as a system of record for who was once assigned to an incident.
Once you resolve the open incidents associated with your user or schedule, you can delete it from your account.